A thyristor is a semiconductor device that has a pnpn structure and carries out a switching operation, and in particular, it has an important function as a high power control device.
FIG. 14 depicts a cross section of a thyristor semiconductor device fabricated per the current art.
A first n-type semiconductor region 101 (N1) is formed on a p-type semiconductor substrate 100, and an electrically insulating layer 102 is formed on regions of a top surface of the first n-type semiconductor region 101.
A second n-type semiconductor region 103 (N2) and a first p-type semiconductor region 104 (P1) are formed at prescribed depths in prescribed regions of the first n-type semiconductor region 101.
A second p-type semiconductor region 105, denoted as an anode AN, is formed on a region of a top surface of the second n-type semiconductor region 103.
A third p-type semiconductor region 107, denoted as a gate G, and a third n-type semiconductor region 108, denoted as a cathode CA, are formed in regions on a top surface of the first p-type semiconductor region 104. Gate G and cathode CA are separated by regions of electrically insulating layer 102.
A first interlayer electrically insulating layer 110, typically composed of silicon dioxide, is formed on a top surface of electrically insulating layer 102, second p-type semiconductor region 105, third p-type semiconductor region 107 and third n-type semiconductor region 108.
Contact holes, denoted CT1, are formed through first interlayer electrically insulating layer 110, reaching second p-type semiconductor region 105, third p-type semiconductor region 107, and third n-type semiconductor region 108. Contact holes CT1 are filled with a first electrically conducting layer, 111.
A second electrically conductive layer 112 is formed in regions on a top surface of first interlayer insulating film 110. Conductive layer 112 contacts conductive layer 111.
A second interlayer electrically insulating film 113, typically composed of silicon dioxide, is deposited over second electrically conductive layer 112 and first interlayer insulating film 110.
Contact holes, denoted CT2, are formed through second interlayer electrically insulating layer 113, reaching second electrically conductive layer 112. Contact holes CT2 are filled with a third electrically conducting material, 114.
A fourth electrically conductive layer 115 is formed in regions on a top surface of second interlayer insulating film 113. Conductive layer 115 contacts conductive layer 114.
In summary, the device depicted in FIG. 14 is a semiconductor with a pnpn structure, in which the first p-type element forms an anode, the second n-type element forms a cathode, and the second p-type element forms a gate; these elements in this configuration form a thyristor.
In this example, the thyristor is switched from high impedance, denoted OFF, to low impedance, denoted ON, by the injection of holes from the anode AN and the injection of electrons from the cathode CA by applying a current to the gate G. Similarly, the thyristor is switched from ON to OFF by turning off the current to the gate G. When the thyrsitor is switched from ON to OFF, time is required for extracting the holes injected into the first n-type semiconductor region 101, so that the turn-off time of the thyristor is lengthened beyond the cessation of current to the gate G. This is a disadvantage of the current art.